There has been a heightened demand in recent years for tamper-evident product containers that readily indicate when a product container has been previously opened. Such tamper-evident containers have proven highly effective in detecting and discouraging pilferage of products in the containers and in alerting a user of possible product contamination.
One common prior art technique for providing tamper-evident containers is to use a supplementary closing element designed for destruction upon the initial removal of a primary closure member. For example, it is known to partially encapsulate the primary closure member with a heat shrinkable plastic that prohibits removal of the primary closure member. In order to remove the primary closure element, it is then necessary to tear or otherwise destroy the heat shrinkable plastic. Another type of supplementary closing element involves a semi-rigid plastic covering secured to the periphery of the container opening and spanning the entire opening. This last mentioned supplementary closing element is disposed beneath the primary closure member and must be removed before initial access to the container contents is possible. Unfortunately, it is possible to completely remove each of the above described supplementary closing elements from the container after accessing the product contained therein. When these supplementary closing elements are completely removed, prior opening of or tampering with the container contents is not readily apparent, particularly to an unsuspecting consumer.
Still another technique for providing tamper-evident containers is disclosed in U.S. Pat. No. 4,431,110 to Roth and U.S. Pat. No. 4,361,244 to Walter. In these prior art patents, a plastic sleeve supports a hinged closure member having a lever portion and a small plug portion to close the container opening. The lever portion of the closure member is initially connected to the cap by a frangible member, designed to be broken during the initial activation of the lever portion to open the container. However, in practice the frangible interconnection between the lever and plug portions may remain intact, without clearly indicating tampering, since the two portions are mechanically attached rather than integrally formed and thus can separate without leaving a tell-tale break. Further, the frangible member of this prior art design is not located at the container opening and thus not prominently visible and may not be noticed, even when broken, by an unskilled or unsuspecting user. Finally, this type of prior art cap is not suitable for a non-liquid product requiring a wide mouth bottle or jar, such as vitamins and health food supplements.